1. Field of the Invention
The present invention relates to electronic control systems used in spas and hot tubs.
2. Description of Related Art
Electronic controls have been developed for spas that give the user effective control of the various electrical equipment, such as motors, lights, and heaters. Typically, a spaside control with a microprocessor is used to manage the overall spa function. The spaside communicates with other components in the control system which turn the equipment on and off according to programming instructions in the spaside and inputs from various sensors. Optional equipments, such as stereo sound systems, are most often separate from the main control system, creating some inconvenience for the user.
Control systems having some integration still make little attempt to physically separate functions for the purpose of troubleshooting and replacement of components. Likewise, it is common to find circuit boards with mixed technology (SMT and thru-hole), due to the need to have high power and low power parts on the same board, which requires extra processing steps for each of these boards.
As electronic spa control systems have become more common, the cost of maintaining these control systems has grown to unacceptable levels. This high cost is attributable to the complexity of design, with higher part counts and attendant failure rates, as well as the need for technicians with greater training.
U.S. Pat. No. 6,756,907B2, Hollaway, teaches the use of built-in diagnostic routines that measure load current, and other parameters, to isolate defective components in a spa. These routines are especially useful in identifying defective motors, heaters, and fuses. The routines are usually started by an operator whenever the spa does not appear to be operating properly.
Some progress has been made to eliminate unreliable components from the control system. U.S. Pat. No. 6,282,370, Cline, et al, teaches the use of two temperature sensors on or near the heater that replaces pressure and flow sensors by turning off the heater if certain temperature profiles are observed, indicating inadequate water flow in the heater. For the Cline invention to work properly, however, both sensors must be placed on the heater and a minimum flow must be maintained. This invention teaches only reactions to a positive difference between the sensor downstream from the heater and the sensor upstream from the heater. If the positive difference is greater than a prescribed amount, it is assumed that there is a flow problem causing the heat buildup. No consideration is made for one of the sensors being defective or for incorrect placement on the heater.
Cline also teaches the use of an independent circuit apparatus to deactivate the heater if a temperature sensor exceeds a predetermined temperature. While this is a useful improvement for providing a backup for the regular high limit control, no provision is made to use the temperature sensors to back up the flow monitoring system.